Formation of Underground Constructions

ABSTRACT

The invention relates to a method and apparatus for the formation of underground structures. The method includes the provision of the formation of at least two spaced support structures which are provided to include a slide track thereon to receive and allow the sliding movement therealong of a roof structure which is moved into position once the support structures are formed to form the underground structure. The support structures can include piled foundations and include a series of units in which the slide tracks are formed. Further articles can be provided to allow the excretion of lubricant to allow the movement of the structure units into position to be improved. Said articles can also be used subsequently to receive a filler material to allow any spaces between the structure and surrounding soil or rock to be filled.

The invention which is the subject of this application relates to improvements in the formation of constructions underground. In particular, although not necessary exclusively, the underground structures are of the type which require excavation work to form the same in a manner in which components to be used to form the structure are advanced into the excavation area. Potential uses of the invention are wide-ranging and include, tunnels, underground rail stations, launch boxes and/or underground car parks.

When forming underground structures using conventional techniques from the surface there is typically a need to disrupt existing services which pass above the area in which the structure is to be formed. This can be expensive in terms of compensatory payments to be made to the operators of the disrupted services as well as causing significant disruption to the public using the services. An alternative system is to excavate under the surface and applying a sprayed concrete lining (SCL) to the exterior surface of the exposed rock and soil of the excavated area in order to stabilise and support the surrounding rock and soil. However, it has been found that several catastrophic failures have occurred when using this system, especially when used with relatively loose soil.

A further problem which is experienced is that as the support structure units are inserted (thrust) into the excavation in the surrounding soil, friction is created between the units and the soil. The degree of friction can become sufficiently large that the units may become damaged and in some cases the frictional forces exceed the jacking capability provided and the units become stuck. It is known to provide ropes or mats which can be placed between the units and soil but these tend to be dislodged and/or moved from the required position, especially with respect to arched units. A further issue is that a tunnelling shield or machine is typically located at the front of the first unit and the excavation takes place within this shield or is performed by this tunnelling machine. The shield or tunnelling machine is manufactured to have slightly larger dimensions than the trailing units in order to provide steering capability and reduce friction of the subsequent trailing units with the surrounding soil However, maintaining this overcut is difficult and the soil above can collapse into the overcut space and create settlement at the surface.

A first aim of the present invention is to provide apparatus and a method which allows the improved formation of underground structures and, at the same time, minimising disruption caused when forming the same. A further aim is to provide apparatus and a method which allows the movement of the units into the excavation to form a tunnel structure and which is improved in terms of improving the ability of the units to be moved more freely through the ground and into position as the excavation proceeds and new units are added. A further aim is to provide an improvement in terms of reducing settlement by providing a means of at least partially filling the overcut space created by the shield. A further aim is, once the units are in place, to allow for the permanent filling of any space above the units thereby limiting future ground settlement.

In a first aspect of the invention there is provided a method of forming an underground structure, said method comprising the steps of excavating soil and/or rock to a sufficient extent to allow the formation of one or more units in position to form at least two, spaced apart, linear support structures, forming and/or exposing linear slide tracks within or on said structures and advancing one or more roof structures into the excavation with respective opposing ends of each of the roof structures in contact with at least one of the tracks and wherein material lying under the one or more roof structures is then excavated to the required depth of the underground structure.

In one embodiment at least the top portion of the support structures is formed from one or more units which are moved into position in a direction substantially parallel to that in which the roof structures are subsequently advanced.

In an alternative embodiment the units are moved down into position from the top surface.

In one embodiment the support structures form piers and abutments. In one embodiment the support structure include a series of the units which are in the form of top wall boxes along the length thereof which form the upper surface of the linear support structures and typically including the slide tracks formed therealong.

In one embodiment the support structures include foundations depending downwardly from the said units. In one embodiment piled foundations are formed and in one embodiment the piled foundations form abutment walls or columns.

In one embodiment the degree of excavation is to a depth which is lower than that of the units in which the slide tracks are formed. This can typically be achieved by the provision of the piled foundations on which the support structure units are positioned.

In one embodiment the support structures include access tunnels formed therein.

Typically, where ground conditions require treatment, the support structures can also be used for pre-stabilization of the ground prior to installing the roof structure.

In one embodiment the roof structure is an arch formation or alternatively the roof structure is a substantially planar deck or beam.

In one embodiment two spaced support structures are provided at a spacing which allows opposing end portions of the roof structures to be placed thereon and supported in position.

In an alternative embodiment three or more support structures are formed and in one embodiment the intermediate support structure can be formed to allow an end portion of each of a first and second roof structure to be placed therealong side by side. In one embodiment each of the roof structures has a transport means located thereunder such as a rail track.

In one embodiment where side by side roof structures are provided, one or more passageways are formed which allow access between the areas under the respective roof structures.

In one embodiment and particularly where space is limited on site, units for the support structure, and/or roof structures will be precast at a factory location and transported to site. Regulations vary from one country to another with regard to the maximum length and width of units that can be transported on public roads. For larger diameter roof structures, such as arches, it would be necessary for these to be cast in two sections i.e. a 3 pin arch or for the two elements to be joined at site to form a 2 pin arch.

It is envisaged that the method is of particular use wherever surface disruption is to be avoided. Where structures have to be constructed with a few meters of cover these techniques are beneficial as they are engineered to minimize any surface settlement. Equally, large deep structures would benefit as the area of exposed face is minimized and a full structural lining is provided at every stage of excavation.

In one embodiment the method includes the steps of forming an access shaft to a required depth and size and then forming the excavated structure in at least one required direction from the access shaft in a substantially linear direction.

In a further aspect of the invention there is provided a structure formed underground, said structure including at least first and second substantially linear support structures, said support structures including a series of units, said support structures spaced apart and each having a track formed therein, said tracks respectively receiving an end portion of at least one roof structure such that said at least one roof structure spans across the space between said support structures and is supported by the same to allow an excavated area thereunder to be defined to a sufficient depth once fully excavated to allow the passage of persons and/or transport means.

In one embodiment the support structures are located in position when the excavated area is of a first depth and, once in position, the excavated area is enlarged with the support structures and roof structures acting as a protective formation in a first function, prior to use for a second function once the excavated area has been fully formed.

In a further aspect of the invention there is provided a method of forming an underground construction, said method comprising the steps of: installing support structures including any of abutments or access tunnel or box, if an access tunnel or box is provided install piling under the same to form abutments and piers, providing slide tracks on each support structure, jacking roof structure units along the support structures with a shield in front of the leading roof structure unit, supporting and sliding the end portions of the roof structure units along the tracks and, as the excavation and shield is advanced, jacking further roof structure units from a launch point at an end of the structure and exposing the slide tracks by removing part of the linear structure.

Typically the exposure of the tracks is matched to the speed of advance of the roof structures.

In a further aspect of the invention, there is provided apparatus for the formation of a tunnel structure in an excavation, said apparatus comprising a plurality of support structure units, supporting a roof structure therebetween, said units formed and located such that when the same are in position, the tunnel structure is created and wherein, there is provided, in position between the external face of the tunnel structure and the surrounding soil or rock, at least one article in which a material is provided to aid the formation of the tunnel structure and/or the stability of the soil or rock around said tunnel structure.

In one embodiment the material is a lubricant which can be excreted from the one or more articles into the interface between said units and the surrounding soil or rock to aid the movement of the units into the excavation.

In another embodiment the material is a grouting or filler material which can be provided to fill any gaps or voids in the soil or rock surrounding the structure.

In one embodiment the articles are used to receive the lubricant during the formation of the structure and then receive the grouting or filler material after the structure is in position.

In one embodiment, the article is an elongate member which extends along the length of the tunnel structure which is formed.

In one embodiment, the article includes the lubricant therein prior to positioning into the interface between the units and surrounding soil or rock or alternatively, lubricant is supplied to the article once in position thereby ensuring that sufficient lubricant is always available. In addition, a flexible filler material may be provided or to at least partially fill the articles but at the same time allow the same to deform in order to cause the lubricant to be excreted therefrom.

In one embodiment, the article is deformable such that when the same is moved into position movement together of the unit and surrounding rock or soil, can cause deformation of the article and cause lubricant or more lubricant to be excreted.

In one embodiment, the said article is provided with a series of apertures or ports at spaced locations on the same, said apertures or ports provided to allow lubricant to pass from the interior of the article to the external faces thereof and hence onto the unit and surrounding soil or rock. Typically, the ports or apertures can increase in size and/or allow increased flow of lubricant in response to deformation of the said article such that the greater the deformation of the article then the greater the flow of lubricant. This is typically due to the fact that if there is increased pressure on the article then it is likely that there will be greater friction between the soil and support structure units and hence a greater need for lubrication to be provided to allow the smooth movement of the unit past the rock or soil which is causing the increased pressure and deformation.

Typically a plurality of the articles will be provided around or adjacent to the external surface of the support structure units.

In one embodiment a plurality of interconnected articles in the form of tubes are cast into the upper surface of each of the units being pushed into place. Each unit will have these cast when manufactured and means are provided to connect the tubes between units when being installed.

Alternatively each array of tubes on a unit can be connected to a separate lubricant/grouting charging unit.

Typically, the diameter of the tubes and the degree of flexibility is determined by specific site conditions. In one embodiment tubes will be embedded into the unit such that the lower part of the tube is rigidly held and the upper part is formed to fill the specific overcut dimensions of a particular tunnel formation.

Typically at least the upper part of the tube will be perforated.

In one embodiment the tubes, during installation, will be charged with suitable lubricant which can be pressurized by pumps located in the outside working area or from within the tunnel to feed lubricant between the tubes and the soil or rock.

Alternatively or in addition any pressure from the overburden soil or live loads at the surface will cause the tubes to deform and cause additional lubricant to be forced between the tubes and soil.

The efficient lubrication reduces the jacking loads required to force the units into the excavation and the ability of the tubes to deform under load allows the tubes to form a flexible mattress between the outer surface, such as the top of the unit, and the soil and will provide a variable and flexible filler to accommodate the differing loads and settlements.

In one embodiment, when all the units are in place the same tubes can be fed and filled with pressurized material which can set, typically permanently and which is herein referred to, in a non limiting manner as “grout” to reform the tubes with pressure and provide a permanent solid filler to the tubes and which can then move into the overcut space to fill any voids between the tubes and the soil and also to solidify the tubes and provide a permanent solid filler in the overcut space.

In one embodiment the grouting can be over pressurised to provide compensation grouting.

Typically, the tubes can be laid at right angles to the line of drive across the units or longitudinally along the unit in line with the drive.

While it is envisaged that the tubes will be provided at least on the upper part of the units and the roof structure, the tubes could also be applied to the sides of the units of a jacked structure especially where it has to be installed close to an existing structure thus providing a flexible spacer and a method of lubrication.

The tubes when positioned thereby cover the upper surface with a “flexible mattress”.

In a yet further aspect of the invention there is provided apparatus for forming a tunnel structure, said apparatus including a plurality of support structure units and/or roof structure units advanced and positioned in series so as to from the structure, wherein said units include at, or adjacent to, at least part of the external surface, a plurality of elongate tubes, said tubes provided to receive lubricant and/or grouting material therein.

In one embodiment at least when the tubes are to receive lubricant, apertures or perforations are provided to allow lubricant to be emitted therefrom. Typically, the lubricant is emitted as the units are jacked into the excavation soil or rock.

Where the tubes are provided to receive grouting material, the material is typically introduced into the tubes once the tunnel structure has been formed. In this case the grouting material is allowed to set and hence at least partially fill any gaps between the external surface of the tunnel structure and the surrounding soil or rock so as to reduce the occurrence of settlement of the soil or rock.

In a further aspect of the invention, there is provided a method of forming a tunnel structure, said method comprising excavating soil or rock to form a path along which the tunnel structure is to be formed, inserting, as the excavation takes place, a series of units, to form support structure and/or a roof structure, and wherein, as the units are inserted, at least one article is also inserted and positioned at the interface between the external face of the units and the surrounding soil or rock, said article provided to receive lubricant and/or grouting material.

Typically, a plurality of the articles are provided the said articles are provided with one or more apertures to allow the lubricant to be emitted therefrom so as to lubricate the interface and hence aid the sliding movement of the units into the excavated area.

In one embodiment the grouting material is introduced once the units are in position.

Typically, a plurality of said articles are provided, and are selectively spaced about said interface.

Typically, the articles are provided as elongate members with a length when joined together, equal or greater than the length of the tunnel structure which is to be formed so as to allow the provision of lubricant along the length of the structure interface. The injection of the lubrication is undertaken to reduce the high friction forces and in an endeavor to fill the overcut. The problems of maintaining lubricant due to it's permeation of the soil and the difficulty in having a lubricant/filler material that will fill the overcut whilst it is being pushed into place is overcome by the provision of the “mattress” of the articles or tubes which allows the flexible filler in the article to deform to accommodate and resist the load and in so doing provides the injection of lubricant where most required.

In whichever embodiment the articles in accordance with the invention can be used in combination to form a “mattress” at the external surface of at least a portion of the structure which is formed. The provision of the articles means that efficient lubrication can be applied between the soil and the jacked units. The fact that the articles are compressible allows the same to act as a filler between the soli and the jacked units in the space which is created by the overcut formed by the shield at the front of the series of jacked units as the excavation occurs and the units are advanced into the excavated area.

Furthermore, once the excavation has been formed, the articles can be filled permanently with a grouting or other filler material which can solidify. The material fills the articles and can be provided at sufficient pressure so as to cause the same to pass through apertures in the articles into any voids in the soil so as to fill the same as well and thereby, when solid, prevent any further soil movement or settlement.

It should be appreciated that while it is possible that the articles in accordance with the invention can be used for the combination of purposes illustrated above, it is possible that the articles may be provided and used for only one, or a combination, of the purposes indicated, and can still be sued t advantage.

Specific embodiments of the invention are now described with reference to the accompanying diagrams; wherein

FIGS. 1 a-f illustrate structures formed in accordance with the invention which have a single span;

FIGS. 2 a-b illustrate double span structures formed in accordance with the invention;

FIG. 3 illustrates a structure formed in accordance with the invention;

FIG. 4 illustrates schematically, the formation of a tunnel structure in accordance with one embodiment of the invention;

FIGS. 5 a-f illustrate the formation of a tunnel structure in accordance with the current invention; and

FIG. 6 illustrates a perspective view of a unit in accordance with an embodiment of the invention.

Referring firstly to FIGS. 1 a-f there is illustrated several embodiments of underground constructions 2 formed in accordance with the invention. In each case the construction includes a series of roof structures 4 which, in the case of FIGS. 1 a-d are arched and typically formed of a series of parts 4′ and in FIG. 1 e is a substantially planar deck or beam. In each case the roof structures are supported via their respective opposing end portions 6,8 on spaced linear, support structures, 18,20. The end portions are supported by placing the same on respective tracks 14,16 formed on the upper faces 10,12 of the support structures 18, 20. When forming the structure the roof structure units 4 are slid along the slide tracks as they are introduced along the same into position as excavation of the area of soil and rock in advance of the leading roof structure progresses. The slide tracks are typically initially enclosed as the support structure is formed and remain enclosed until the same are progressively exposed as the roof structure units are advanced along the same. The aim of this procedure is to prevent the ingress of dirt or rocks onto the slide track and thereby ensure that the slide tracks are in as good a condition as possible to aid the movement of the roof structure units therealong.

In one embodiment the top portions 22 of the linear support structures are provided, at least initially, with an access passageway therealong in order to allow personnel and/or apparatus to be moved therealong to the front of the structures.

The support structures can include a number of units which can be introduced in position in a first excavated area typically by advancing the same in sequence along the paths in which the support structures are to be formed. Typically only sufficient soil or rock has to be removed to accommodate the positioning of the units which are to be used to form the linear structures and the roof structures 4 which are to be slid along the tracks 14,16 on the installed support structures 18,20 such that one the support structures are formed the roof structures can then be advanced into position.

In the embodiment of FIG. 1 a the support structures 18,20 comprise a series of units 21 which have been preformed and moved into position and piling foundations 24 which are formed to depend downwardly from the units 21 to form the support structures 18,20. This arrangement means that the depth X of the tunnel structure can be greater than the depth of the units 21, if required, with the depth of the same being formed to suit specific purposes of use of the structure once formed. Typically the depth is excavated once the roof structure is in position.

In FIG. 1 b, there is shown a further embodiment in which the support structures 18,20 are formed by runnel structures which act to support the arched roof structure units 4 and also a base deck 23 thereon. In this case the support structures are wholly formed from the units 21 which are advanced into position initially to form the slide tracks along which the roof structure can be advanced. FIG. 1 f illustrates a further variation on the arrangement of FIG. 1 b in which the units 21 for each support structure 18,20 are formed as a bored tunnel and load bearing piles 24 are then formed downwardly from the access passageway 25 formed within the units 21. Slide tracks 14 16, in this case formed by pumping concrete along the access passageways, are then formed along the interior of the support structure units 21. Once the slide tracks are formed portions of the support structure units 21 are then progressively removed to allow the slide tracks 14,16 to be exposed and the leading shield which allows the excavation to be performed is slid along the tracks as the excavation is performed, followed by the roof structures 4 as indicated by arrow 33 until the roof structure is formed in position.

FIG. 1 c illustrates a similar arrangement to that of FIG. 1 b with the units 21 of the support structures being box shaped instead. In both cases access passageways 25 can be provided along the length of the support structures. FIGS. 1 d and e illustrate arrangements where the support structures 18,20 are formed of units 21 similar to the other embodiments and then a series of foundation units 27,29, all of which can be jacked into position to form eth support structure.

In each embodiment when the support structures are in position, the slide tracks 14,16, which are initially covered over, can be exposed progressively as the roof structures 4 are moved along the same. Thus the first roof structure is placed in position with an excavating shield in advance of the same. As the excavating progresses so the tracks 14, 16 on the linear structures can be successively exposed under the protection of the excavating shield, which is at the front of the roof structures. This means that the slide tracks, which are initially covered over and protected by lids or other covering means and hence protected during the excavation work, need only be exposed when necessary to receive the advancing roof structures 4 and the tracks, once exposed, are protected by the shield from debris and the like, thereby easing the smooth progression of the roof structures along the tracks as they are jacked along the same by jacking apparatus. Once the roof structures 4 are in position along the linear structures 18,20 further excavation can be performed under the same to form the excavated area to the required depth with the work done safely as it is protected by the construction which has been formed and without need to disturb the top surface of the area being excavated.

FIGS. 2 a and b illustrate further forms of constructions which can be formed in a similar way to those of FIGS. 1 a-e with the exception in that in these embodiments a double span roof structure 104 is formed with the ends 6′, 8′ of the adjacent roof structures being supported along a common intermediate support structure 120 as shown. Typically, access passages 122 are provided between the adjacent roof structure areas as shown. In FIG. 2 a the support structure units 21 form each of the support structures, 18,20,120 and in FIG. 2 b the support structures are formed by the units 21 mounted on pilings 24 formed to the required depth.

The constructions in accordance with the invention can have many uses, one of which is shown in FIG. 3 for use in the accommodation of underground rail tracks 125. The construction, which could be used in the formation of an underground rail station, for example, in this case the construction accommodates a single track 125 with platform 126 and are typically 6.2-6.7 diameter.

A central platform of the type which would be formed at the intermediate support structure 120 requires a minimum 6 m plus two tracks so a 14 m arch roof structure would be sufficient.

For the arrangements shown in FIGS. 2 a-b and FIG. 3 the structures are based on a 12 m width between platforms which would accommodate twin tracks with wider trains than London underground.

The length of station is determined by the platform length required to accommodate the number of carriages. In FIG. 3 the station shown is based on driving in both directions from a central excavation which would be the access concourse.

In one embodiment a structure can be formed and used as a “launch” box to provide an underground access to which apparatus can be moved and from which the same can be launched to construct the tunnels running off in one or more directions therefrom. They then provide the basic structure within which the permanent station is constructed.

Typically these will be 22-24 m span and around 200 m long. The height will be determined by the diameter of tunnel to be driven but for a twin track tunnel this could be 6/7 m diameter so internal depth of box could be up to 8-10 m. The length of these boxes are around 200 m

In one embodiment the structures are derived from a central access shaft 128 in both directions using the method described herein to give the clear spans required. The central access shaft can also be used to provide further services such as access from street level, ticketing facilities and the like as shown with the shaft 128 in communication with an above ground “station” 130 as shown in FIG. 3

In another form of use both the jacked arch and jacked deck could be used to create underground parking below streets, buildings, parks etc and in which a series of interconnecting bays would be created either using an arch or a jacked deck roof structure.

To provide parking bays either side of a central access road require typically a clear span of 10-12 m for each bay.

A yet further use is as an underground storage cavern for use by a number of developers and industries that have a need to create storage space in locations where open cut excavation would be too disruptive or not cost effective. These could be constructed by the jacked arch and deck techniques.

There is now described apparatus and a method for use in the forming of the structures as herein described which can be used to advantage in the embodiments of structure described herein and also in the formation of other forms of structure in which one or more units are required to be moved into an excavated area of soil and/or rock. With regard to FIG. 4, there is illustrated a body of soil into which a tunnel structure 204 is being formed. The tunnel structure 204 is being formed from a series of units 206 which are slideably moved into the excavated area 218 as the excavation increases in length. Each of the units in this embodiment is used to support a roof structure 210 of the tunnel structure, although this need not always be the case, such that the free space between the units and top portion 209 , when the units are combined, form the free space of the tunnel structure. It will be appreciated as the units are moved into position, friction can be created between the interface of the surrounding soil or rock which can prevent the sliding movement from occurring easily or indeed at all. This can cause significant delay in the formation of the structure and/or cause damage.

In accordance with the present invention, when forming the tunnel structure, such as, for example that shown in FIG. 4 or the structures of FIGS. 1 a-e, 2 a-b and/or FIG. 3, articles in the form of tubes 210 are provided and are spaced around the interface between the external faces of the units 206 and the surrounding rock or soil 218. These articles are typically embedded prior to installation within the concrete of the support structure units 206 at the time of casting. The tubes are perforated to allow lubricant/grout to be dispensed, and the tubes on adjacent units can, in one embodiment be selectively joined to allow the flow of lubricant therealong.

The articles 210 are shown in more detail, in cross section, in FIGS. 5 d-f and include a lubricant material contained therein typically in a liquid form and have a series of apertures or ports 212 formed along the length thereof such that lubricant can leave the elongate members as the unit 206 in which they are provided moves into and along the excavation in direction 214 as shown in FIGS. 5 a-b and hence provide lubrication of the interface 216 between the unit 206 and the surrounding rock or soil 218 and hence improve the sliding movement of the units.

In one embodiment, the lubricant 220 may be allowed to leave the elongate members even when the same are in an uncompressed form as shown in FIGS. 5 a and 5 d but typically, the extent of lubricant 220 which leaves the article at any given time, is increased by the pressure which is exerted on the members such as, by the unit or surrounding rock or soil. This pressure causes deformation of the elongate member which in turn, squeezes more lubricant out of the elongate member at that location and hence provides more lubricant at the location at which it is most likely to be required. The deformation of the tubes 210 will vary accordingly in respect of to external loading and provide resistance to settlement.

On completion of the installation the tubes 210 can be permanently filled with a grouting material 222, or a similar material encompassed herein by the term “grout”, under pressure to reform them and also force grout through the apertures 212 into any voids between the surrounding soil and the external surface of the units 206.

FIG. 6 illustrates a further form of unit 206 and illustrates in this case the tubes or members 210 located along the top face 224 and side faces 226, 228 of the unit. In this case the tubes 210 extend in the line of drive 214 of the unit into the excavation, although, in another embodiment the tubes can be provided to extend at right angles to the direction of drive.

The provision of these articles and the combination of the articles as described herein allow the reduction of the risk of excess friction as the units are jacked into position, reduces the risk of surface damage to surface structures due to settlement and soil movement being created by the jacking of the units and the installation which is created.

There is therefore provided in accordance with this invention a method and apparatus which can be used to improve the formation of underground structures. 

1. A method of forming an underground structure, said method comprising the steps of excavating soil and/or rock to a sufficient extent to allow the formation one or more units in position to form at least two, spaced apart, linear support structures, forming and/ or exposing linear slide tracks within or on said structures and advancing one or more roof structures into the excavation with respective opposing ends of each of the roof structures in contact with at least one of the tracks and wherein material lying under the one or more roof structures is then excavated to the required depth of the underground structure.
 2. A method according to claim 1 wherein the support structure include one or more units which are moved into position in a direction substantially parallel to that in which the roof structures are subsequently advanced.
 3. A method according to claim 1 wherein the support structures include one or more units which are moved down into position from the top surface.
 4. A method according to claim 2 wherein the units form support structure piers and abutments.
 5. A method according to claim 2 wherein the support structure units are positioned along the support structures to form the upper surface of the support structures and which include the slide tracks formed therealong.
 6. A method according to claim 1 wherein the support structures include piled foundations which depend downwardly from a series of units in which the slide tracks are formed and which form abutment walls or columns of the support structure.
 7. (canceled)
 8. A method according to claim 1 wherein the support structures include an access therealong.
 9. A method according to claim 8 wherein the slide tracks are formed in the access once the tunnelled access is formed.
 10. A method according to claim 1 wherein the support units are provided along a tunnel which is formed to form the support structure, and which includes an access therealong from which pilings depend and in which the slide tracks are formed.
 11. A method according to claim 1 wherein two spaced support structures are provided at a spacing which allows support of the opposing end portions of the roof structures placed thereon.
 12. A method according to claim 1 wherein three or more support structures are formed and include an intermediate support structure on which an end portion of each of a first and second roof structure is placed therealong.
 13. A method according to claim 1 wherein once at least the support structures are formed excavation is performed to form the space between the same down to the required depth.
 14. A method according to claim 13 wherein the excavation is performed as the roof structure is moved into position and/or once in position.
 15. A method according to claim 13 wherein the excavation is performed to a depth which is greater than that of the units of the support structure.
 16. A method according to claim 1 wherein an access shaft is formed to a required depth and size and then forming the excavated structure in at least one required direction from the access shaft in a substantially linear direction.
 17. (canceled)
 18. (canceled)
 19. A method according to claim 15 wherein a shield is provided in front of the leading roof structure unit and the slide tracks are exposed when they lie under the said shield and are protected thereby.
 20. A method according to claim 1 wherein there is provided in a space formed between the external face of the support structure units and or roof structure units at least one article containing a material for use in aiding the advancement of the said units into position, and/or stabilising said space and adjacent soil or rock once the structure is formed.
 21. A method according to claim 20 wherein the said material is a lubricant which is excreted from the said at least one article as the units are moved into position in order to lubricate the passage of the units.
 22. A method according to claim 20 wherein the material is a grout which is introduced into the at least one article once the structure is formed, said grout hardening when in position.
 23. A method according to claim 20 wherein the said at least one article includes lubricant initially as the same is moved along with the units into the excavation and, following the movement into position, any remaining lubricant is moved and the article is filled with the grout material.
 24. (canceled)
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 27. A structure formed underground, said structure including at least first and second substantially linear support structures, said support structures including a series of units, said support structures spaced apart and each having a track formed therein, said tracks respectively receiving an end portion of at least one roof structure such that said at least one roof structure spans across the space between said support structures and is supported by the same to allow an excavated area thereunder to be defined to a sufficient depth once fully excavated to allow the passage of persons and/or transport means.
 28. A structure according to claim 27 wherein the linear structures are located in position when the excavated area is of a first depth and, once in position, the excavated area is enlarged with the linear structures and roof structures acting as a protective formation in a first function prior to use for a second function once the excavated area has been fully formed.
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